Uhm... are you really looking at a Plasma / LCD?
For that price you really have to be looking at a back projection TV and/or DLP which is another story. For DLP/Back projection I have no idea since they're extremely rare here in Europe (at least in Nordics) most likely because of their poor performance and Plasma/LCDs are getting cheaper all the time. If you want to stay at your current price range I'd say without a doubt Panasonic TH-42PX600 (PX60 is slightly cheaper but without some extras such as front speakers and card reader, the speakers are in the back instead). It's a very good plasma TV for its price and it are praised by both reviewers and home users (avsforum.com). 50" is around 1500$ (PX60) so its a bit more expensive....
To be honest I dont think you should have a look at LCDs as it seems you want as large as possible, at least I get that impression.
If you're going to consider LCDs I'd highly recommend Sharp LC-42D62U, its quite expensive but you'll get an awesome TV with 1080p (which also is supported if you want to hook up a computer to it). You can find lots of information about it at avsforum.com although it is noticably more expensive than the Panasonic plasmas.
If you want to have a discussion about it feel free to ask, I'm pretty "knowledgeable" when it comes to TVs :-)
//Danne